A conventional pulse generating circuit is actually a comparator. A working principle thereof is that an input signal Vin is compared with a reference voltage Vref; and when Vin>Vref, 1 is output; otherwise, 0 is output. In this way, a periodic triangular wave signal is converted to a pulse signal. In some application, considering hardware system overheads, a quite high frequency pulse is not required. Therefore, a frequency of a pulse generating circuit needs to be limited. However, at present, there is no pulse generating circuit for limiting a highest frequency.